Organic electronic devices are articles that include layers of organic materials, at least one of which can conduct an electric current. An example of an organic electronic device is an organic light-emitting diode (OLED). OLEDs typically consist of an organic light emitter layer and optional organic charge transport layers on both sides of the emitter disposed between two electrodes: a cathode and an anode. OLEDs, sometimes referred to as lamps, are desirable for use in electronic media because of their thin profile, low weight, and low driving voltage, e.g., less than about 20 volts. OLEDs have potential use in applications such as backlighting of graphics, pixelated displays, and large emissive graphics.
A “roll-to-roll” method for making OLED devices includes forming the various layers on a web substrate. In order to provide the proper arrangement of the various layers such as providing the cathode electrically isolated from the anode, multiple deposition and patterning steps are employed to manufacture the ultimate device structure. In particular, it is common practice to pattern the anode (e.g. indium-tin oxide), such as described in U.S. Pat. No. 6,410,201 and U.S. Pat. No. 6,579,422.
A problem associated with the development of larger area OLEDs is the presence of local defects that cause electrical shorts. Causes of shorting defects include, for example, particle contamination during fabrication, surface roughness often contributed from the electrode, and non-uniformities in the organic layer thickness. Local defects initially present as a result of fabrication imperfections are typically present as small non-emissive, non-conducting areas at the location of the electrical short. One approach to this problem is described in Applied Physics Letters, vol. 82, no. 16, Apr. 21, 2003 entitled “Fault-tolerant, scalable organic light-emitting device architecture”. This article describes that, “Another obstacle to achieving large area devices results from the fact that OLEDs are current driven, i.e. brightness scales with current density. Thus, larger devices require a greater current to spread throughout the active area.” This article addresses both of these obstacles to large area devices by fabricating a number of smaller light-emitting elements connected in series on a monolithic substrate.
Although various OLED structures and methods of manufacture have been described, industry would find advantage in improved structures and methods of manufacture.